1. Field of the Invention
The present invention relates to document security and, more particularly, to preventing a user from obtaining a copy of an entire document.
2. Description of the Background Art
It is easier to make a copy of information in electronic form than it is to make a copy of information in physical form. This fact makes content owners wary of making their electronic information accessible by the public. However, content owners desire to provide their content to users, often for a fee, and would benefit by having this information be searchable, in order to assist users in finding content that matches their interests and needs. Users of search engines in particular expect to be able to view the relevant portions of a document or other content prior to purchasing the content. However, providing users access to the relevant portions typically results in giving users access to the entire document in a way that allows the user to make a copy of all of the content without paying for it.
Alternatively, it is possible to prohibit users' access to the relevant portions of a document until payment is received. However, in that situation, users are unable to see the relevant portions of the document and thus cannot best judge whether the document satisfies their interests or needs and, as a result, are less likely to purchase the content.
Various other technologies have been developed with the goal of allowing a user to view a document while preventing the user from making a copy of it. One possibility is to allow a user to view only a portion of the document. If the user is allowed to choose which portion, however, a team of users can obtain an entire document by coordinating efforts and requesting different portions. Another possibility is to monitor accesses to the document and try to detect attacks. Unfortunately, dynamically and rapidly monitoring data accesses is very difficult to implement.
Other technologies developed to allow a user to view a document while preventing him from making a copy of it include, for example, modifying the user's browser to disable printing and specifying that an image, if printed, should be blank. While many technologies exist, each of them can be circumvented.
What is needed is a way to allow a user to view an electronic document while preventing the user from making a copy of the entire document.